1. Field of the Invention
This invention relates generally to doctors used in papermaking machines, and is concerned in particular with the provision of a blade holder which is readily separable from the doctor back and removable from the papermaking machine for cleaning, inspection and repair.
2. Description of the Prior Art
The main components of a doctor system include the doctor blade, the blade holder, the doctor back and the loading mechanism. The doctor blade keeps the roll clean and/or sheds the sheet. It must be perfectly flat, straight and parallel, and its composition must be compatible with the roll to be doctored.
The blade holder exerts a uniform, designated load pressure on the blade. It holds the blade firmly against the roll, accommodates roll irregularities and, within limits, compensates for thermal expansion.
The doctor back is in essence the backbone of the doctor. It serves as the support structure for the blade holder. The loading mechanism pivots the doctor back to load the doctor blade against the roll.
Doctor blade holder designs used in recent years are more complex and have more components than the simpler blade holders used in the past. As a result, the more recent holder designs require more routine cleaning and maintenance.
As disclosed for example in U.S. Pat. No. 5,980,692 (Goodnow et al.), it is known to provide removable blade holders which allow for cleaning and maintenance to be performed off line while the papermachine continues to operate with a replacement blade holder.
Experience has indicated, however, that removal of the blade holder is sometimes made difficult due to frictional resistance between mating sliding surfaces.
The present invention addresses this problem by mechanically interlocking the blade holder to the doctor back with rotatable elements. The rotatable elements are strategically positioned to reduce frictional resistance to blade holder removal and replacement.
This and other objectives, features and advantages of the present invention will now be described in greater detail with reference to the accompanying drawings, wherein: